Chlorinated hydrocarbon compositions and uses thereof

ABSTRACT

A composition for cleaning and drying articles comprising a chlorohydrocarbon solvent and a metal, ammonium or amine salt of an alkyl benzene sulphonic acid wherein the alkyl group contains from seven to 14 carbon atoms.

ited States Patent 1 Johnson 1 CHLORINATED H YDROCARBON COMPOSITIONS ANDUSES THEREOF [75] Inventor: Peter Graham Johnson, Cheshire,

England [73] Assignee: Imperial Chemical Limited, London, England [22]Filed: Sept. 23, 1970 [2]] Appl. No.: 74,912

Industries [30] Foreign Application Priority Data Oct. 7, 1969 GreatBritain ..49,275/69 [52] US. Cl. ..252/545, 252/153, 252/558 [51] Int.Cl. ..'...Clld 1/18, Cl 1d 1/50 [58] Field of Search..252/152,l53,16l,l62,171,

[5 6] References Cited UNITED STATES PATENTS- 3,336,232 8/1967 Bauer etal. ..252/153 H11 ums 1 Jan.30,1973

OTHER PUBLICATIONS Gafac-Phosphate Ester Surfactants as Dry-CleaningDetergents, GAF Bulletin, N.Y., i963, p. 3.

Primary Examiner-Leon D. Rosdol Assistant Examiner-P. E. WillisArtorneyCushman, Darby & Cushman [57] ABSTRACT A composition forcleaning and drying articles comprising a chlorohydrocarbon solvent anda metal, ammonium or amine salt of an alkyl benzene sulphonic acidwherein the alkyl group contains from seven to 14 carbon atoms.

10 Claims, No Drawings CHLORINATED HYDROCARBON COMPOSITIONS AND USESTHEREOF This invention relates to chlorinated hydrocarbon compositionsand uses thereof, and particularly to compositions "comprisingchlorohydrocarbon solvents and surface-active agents and use of suchcompositions for cleaning and drying articles, for example machinery,

instruments and other metal articles, plastic articles which are noteffected by the solvent for example polyamides, polypropylene andpolytetrafluoroethylene, textile-materials and glass articles generally.

It is well known that liquid chlorinated aliphatic hydrocarbons have theproperty of dissolving grease and oils, and that they can be used toeffect degreasing of metals and other articles. It is also well knownthat the chlorinated aliphatic hydrocarbons, especiallytrichloroethylene and perchloroethylene, can be used to dry metal andother articles since the boiling solvents have the property of removingwater from articles in the form of a constant boiling mixture with thesolvent. The constant boilingmixture of trichloroethylene and watercontains 13 parts by weight of trichloroethylene and 1 part by weight ofwater, and that of perchloroethylene and water contains 5 parts byweight of perchloroethylene and 1 part by weight of water.

In drying processes using these solvents, water can be removed simply bydistillation since the-constant boiling mixture boils ata temperaturelower than the boiling point of the pure solvent. The resulting vaporsare condensed and the condensate is passed to a water separator whereinthe solvent is recovered for re-use. The method can be carried outefficiently in view of the appreciable water content of the constantboiling mixture.

However, processes for drying articles using pure or conventionallystabilized trichloroethylene or perchloroethylene have the disadvantagethat the surface of the article tends to become stained due to in situdrying of water droplets. This effect is particularly noticeable inthedrying of metal and glass articles. In order to overcome thisdisadvantage it is necessary that the water droplets be removed from thesurface of the article and incorporated in the solvent prior to theirevaporation.

Moreover, while the chlorinated hydrocarbon solvents, particularlytrichloroethylene and perchloroethylene have the property of dissolvingoils and greases they do not remove water-soluble contaminants. It isclearly desirable, therefore, to increase the potential uses of thesesolvents by using them in admixture with water, but simple physicalmixtures of these solvents and water are not effective as cleaningagents. We have found that the properties of the chlorinated hydrocarbonsolvents can be modified to confer upon them the property of taking upwater in the form of an emulsion of water in the solvent (a water-in-oilemulsion) by incorporating therein a metal, ammonium or amine-salt of analkyl benzene sulphonic acid wherein the alkyl group contains from sevento 14 carbon atoms. These salts are commonly known as alkyl benzenesulphonates and we have found that they are efficient in enablingappreciable amounts of water to be emulsified in chlorinated hydrocarbonsolvents.

According to the present invention we provide a composition comprising achlorohydrocarbon solvent and a metal, ammonium or amine salt of analkyl benzene sulphonic acid wherein the alkyl group contains from sevento 14 carbon atoms.

Particularly good results have been obtained using salts of alkylbenzene sulphonic acids wherein the alkyl group contains ll, 12 or 13carbonatoms (straightchain or branched-chain) i.e. undecyl-, dodecylandtridecylbenzene sulphonic acids. We prefer to employ a salt which issoluble in the chlorohydrocarbon solvent. Where the salt is a metalsalt, the metal is preferably an alkaline earth metal, notably calcium.A particularly suitable metal salt .for incorporation intotrichloroethylene is the calcium salt of tridecyl benzene sulphonicacid.

A wide variety of amines may be used to form the salt of the alkylbenzene sulphonic acid. Amines which can be used include the primary,secondary and tertiary alkylamines or alkanolamines, aromatic amines,cyclic amines and heterocyclic compounds containing N as heteroatom.Particularly suitable amines, however, are methylamine and ethylamineand especially suitable saltsare the methylamine salts of dodecylbenzene sulphonic acid and tridecyl benzene sulphonic acid, and thetriethylamine salts of undecyl benzene sulphonic acid and dodecylbenzene sulphonic acid.

Particularly suitable ammonium salts which may be used are the ammoniumsalts of undecyl benzene sulphonic acid and dodecyl benzene sulphonicacid.

Solutions of the salt in the solvent have the property of emulsifyingwater and forming a water-in-oil emulsion.

According to a further feature of the invention we provide a compositioncomprising a chlorohydrocarbon solvent, a metal, ammonium or amine saltof an alkyl benzene sulphonic acid wherein the alkyl group contains fromseven to 14 carbon atoms, and water. Depending on the amounts of waterand the salt in the composition, the emulsion may be clear and stable orit may be milky with a tendency to instability. in particular we havefound that there is a critical ratio of water to the salt below whichthe emulsion is clear and stable and above which the emulsion is milky.There is a particular critical ratio of every combination of salt andsolvent employed and this can be readily determined by simpleexperiment. As a general guide, however, the critical ratio ofwaterzsalt in emulsions in trichloroethylene is about 1.5:1 although theratio may vary in the range say'0.8:l to 1.821 depending on theparticular salt employed. As a further guide the critical ratio of.waterzsalt' in emulsions in 1,1 ,l-trichloroethane is ofthe order of3:1.

By way of example, an emulsion in trichloroethylene of 1' part by weightof ammonium dodecyl benzene sulphonate and 1 part by weight of water isclear and transparent and is stable for prolonged periods. On the otherhand, an emulsion in trichloroethylene of 1 part of calcium tridecylbenzene sulphonate and 60 parts by weight of water is a milk in whichphase separation commences within a few hours if the emulsion is allowedto stand without agitation.

The compositions which contain water, particularly those containingappreciable quantities of water and which are either clear or milky areuseful as cleaning agents for articles immersed therein; the articlesare freed from grease and oils, and also water-soluble contaminants.

We have found that for practical cleaningpurposes the amount of waterwhich is emulsified in the solvent should preferably be at least 1percent by weight but need not be greater than about 60 percent byweight of the resulting emulsion. in order to be capable of emulsifyingthis amount of water and forming a water-in-oil emulsion there is noadvantage in using a total amount of surface active agent greater than33 percent by weight based on the weight of the emulsion and we havefound that for most practical purposes the total amount of surfaceactive agent need not exceed percent by weight based on the emulsion.

The composition should preferably contain at least 0.1 percent by weightof the salt and in the case of clear emulsions the amount of the saltshould preferably be at least 1 percent by weight.

Other substances may be incorporated in the compositions instead of butpreferably in addition to water, in which case it is preferred to have aclear emulsion. Examples of such other substances are ammonia, hydrogenperoxide, phosphoric acid, hydrochloric acid and metal chelating agents.Dyestuffs may also be incorporated in the compositions. The amount ofsuch substances which can be tolerated in emulsions of water in thechlorinated hydrocarbon solvent is limited by their causing phaseseparation of the emulsion when present in appreciable quantities. Themaximum amount of the substance which can be tolerated in clearemulsions depends upon the particular substance and can be determined bysimple experiment.

The compositions of the invention may be used as drying agents in whichcase they are preferably substantially free from water, although this isnot essential providing the composition is clear. The water-freecomposition should preferably be capable of emulsifying large amounts ofwater to form a clear emulsion and the amount of the salt can be asdescribed above in respect of cleaning agents.

The chlorohydrocarbon solvent constituent of the compositions can be anyliquid chlorohydrocarbon solvent, especially a chloroaliphatichydrocarbon for example trichloroethylene, perchloroethylene, 1,1,1-trichloroethane, beta-trichloroethane, cis and trans dichloroethylenesand methylene dichloride.

We have found that only a limited amount of electrolytes can beincorporated in the clear emulsions of the invention since appreciableamounts of electrolytes cause a portion of the water to separate outinto a distinct layer when the composition is allowed to stand, forinstance overnight, without any form of agitation. If this phaseseparation occurs the separated water layer can be discharged and ifappropriate fresh water can be added before the composition is re-used.Separation of the emulsions due to the presence of electrolytes is oftenan advantage since, after the separation, the electrolyte is present inthe water layer and can be removed with that layer. Thus, for example,electrolytes entering the emulsions during cleaning of articles maycause separation of the emulsion during periods when the emulsion is notbeing used. Removal of the separated water layer, for example byskimming, thus removes the electrolytes from the treatment vessel and sorisk of redeposition of electrolytes on the article to be cleanedsubsequently is reduced, thus enabling stain-free cleaning of articlesto be achieved even if those articles are contaminated with metal saltsand electrolytes. We

prefer to use distilled or de-ionized water in the cleaning compositionsof the invention.

Similarly in the drying of wet articles any electrolyte entering thecomposition together with appreciable amounts of water will cause thewater to separate out when the composition is allowed to stand withoutagitation. If desired water may be added at the end of the dryingoperation to achieve this effect.

If required the compositions of the invention may contain one or morestabilizers. Stabilization may be required against decomposition of thesolvent induced by the presence of metals, (especially aluminum andzinc) and/or by heat and light. For example it may be necessary tostabilize the solvent to inhibit attack on metal articles being cleanedor dried or on the materials of construction of the cleaning or dryingand rinsing tanks. Any of the known stabilizing additives forhalogenated hydrocarbon solvents may be employed to prevent thesedecomposition reactions. Examples of such stabilizing additives arenitroalkanes and other alkyl and aryl nitro-compounds, epoxides, aminesfor example triethylamine, alkanolamines, cyclic ethers, ketones,substituted phenols, pyrroles and alcohols for example propargylalcohol. Usually the total amount of stabilizers added will not exceed10 percent by weight of the composition. In addition to stabilizers,compounds known to inhibit tarnishing of copper and brass may be added.

Cleaning or drying of articles using the appropriate composition iscarried out in the case of clear compositions simply by immersing thearticles in the composition for a suitable period of time, for exampleseconds. The article is then removed and will generally be rinsed in apure solvent (conveniently the same solvent as is used in thecomposition) to remove traces of the alkylbenzene sulphonic acid salt orother additives which may have become deposited on the article. Whencleaning with compositions which are milky, it is preferred to spray thecomposition on to the workpiece and/or to agitate the composition.Cleaning compositions which are clear can be used at their boilingpoints, thus producing sufficient agitation of the composition, both inthe cleaning and in the rinsing treatments, but if desired lowertemperatures, conveniently room temperature, can be used in conjunctionwith ultrasonic agitation. .Compositions which are milky are preferablynot used at their boiling points although they can be used at slightlyelevated temperatures for example up to about 40C. Also, after cleaningwith a milky emulsion, the first rinse is preferably carried out in coldsolvent. Preferably, where the rinsing is carried out in cold solvent, afurther rinse in boiling solvent or in solvent vapor is carried outsince this enables the solvent to evaporate quickly from the articleafter rinsing. Drying compositions (which are preferably clear) willusually be used at the boil, but they can be used at lower temperaturesin conjunction with ultrasonic agitation. After drying, the articleswill be rinsed as described above.

The articles, after treatment to clean or dry them have surface activeagent deposited on them and this deposit is removed in the rinsetreatment.

The water-free compositions and the clear emulsions of the invention arestable on storage and are usually colorless transparent liquids even atthe boil and after refluxing for prolonged periods. The compositions(clear or milky) are prepared very easily by adding the salt of thealkylbenzene sulphonic acid to the solvent and stirring the mixture todissolve the salt. In the case of cleaning compositions water is thenadded with stirring. The water content of the compositions is veryeasily adjust by adding water to increase the content or by strippingwater from the composition, for example by distillation or by adding anelectrolyte followed by skimming off the resulting water layer, todecrease the water contentfNormally, using a boiling clear compositionto dry articles there will be little or no water in the compositionafter use unless a large batch of wet articles is dried immediatelyprior to switching off the heat supply to the drying bath.

The compositions of the invention which contain water (whether clear ormilky) can be used to clean metal (though special additives may benecessary to prevent corrosion of the metal), insoluble plastics, glass,textile materials and other articles and the waterfree compositions canbe used to dry such articles. Cleaning results in the removal of greaseand oil and water-soluble dirt. Drying results in the removal of waterfrom the articles. Thedrying compositions are particularly useful, forexample, for drying metal articles following electroplating processes.

The invention is illustrated but in no way limited by the followingexamples, wherein all parts and percentages are by weight unlessotherwise stated:

EXAMPLE 1 4.0 parts of ammonium dodecyl benzene sulphonate were added to90.0 parts of a commercially available grade of trichloroethylenecontaining stabilizers and the mixture was agitated. Distilled water wasthen added and the mixture again agitated to form a clear water-in-oilemulsion, the amount of water being such as to give an emulsioncontaining 6 percent of water based on the total emulsion. The emulsionwas then used to clean articles by the following procedure.

The emulsion is placed in a tank provided with means (e.g. a transducer)for ultrasonic agitation of the composition. Trichloroethylene(commercially available grade containing stabilizers) is poured intoboth compartments of a two-compartment tank which is separated from thetank containing the emulsion. In the two-compartment tank thecompartments are in communication through a horizontal slit in theircommon wall. One of the compartments (the rinsing compartment) isprovided with means (e.g.- a transducer) for ultrasonic agitation of thesolvent in the compartment, and the other (the vapor compartment) isprovided with a heater to enable the solvent therein to be boiled. Thevapor compartment is provided close to its upper end with cooling coilstocondense the vapor emitted by the boiling solvent and to form a vaporzone above the surface of the boiling solvent. Pure solvent'is pouredinto the vapor compartment to a level below the slit in the'common wall,and in the rinsing compartment to a level such that a slight flowresults through the slit into the vapor compartment. Means are providedfor collecting the liquid solvent condensing from the cooling coils ofthe vapor compartment and passing this liquid solvent to the rinsingcompartment.

The article to be cleaned is immersed for about 30 seconds in thewater-in-oil emulsion which is ultrasonically agitated. The cleanedarticle is then immersed for about 30 seconds in the pure solvent whichis ultrasonically agitated in the rinsing compartment. The article isthen held for about 30 seconds in the vapor zone of the vaporcompartment in which the solvent is boiling. The article is removed fromthe vapor and it dries rapidly.

By this procedure a wide variety of articles have been cleaned,including for example metal pressings and extrusions, 'wire drawingdies, spinerettes, polished metals, silicon slices, lenses andmicroscope slides. In each case the cleaned articles were completelyfree from grease, oils and water-soluble dirt, and they were also freefrom drying stains.

EXAMPLE 2 A drying composition was prepared by adding 2.0 parts ofammonium dodecyl benzene sulphonate to 98.0 parts of stabilizedtrichloroethylene and agitating the resulting mixture. The compositionwas then used to dry articles by the following procedure:

The composition is placed in one of the compartments of atwo-compartment tank in which the compartments are in communication by ahorizontal slit in the common wall. The upper level of the compositionis below this slit and stabilized trichloroethylene is poured into theother compartment (the rinsing compartment) to a level such that aslight overflow results through the slit into the composition. The twocompartments are provided with heating coils to enable the compositionand the pure solvent to be boiled. Cooling coils are provided tocondense vapors emitted from the compartments as a result of thisboiling, means being provided for passing the total condensates(consisting of pure solvent initially but also water once a wet articlehas been introduced into the drying composition) to a water separatorfrom which the pure solvent can be returned to the rinsing compartment.

Both the drying composition and the pure solvent in the rinsingcompartment are boiled continuously and the wet article to be dried isimmersed in the drying composition. The composition froths initially butthe froth rapidly disperses. After a suitable period of time, usuallyabout 30 seconds, the article is removed from the composition and isimmediately immersed in the pure solvent in the rinsing compartment,again for a period of about 30 seconds. The dried article is thenremoved from the rinse liquor. During this drying procedure, condensedsolvent is continuously introduced into the rinsing compartment from thewater separator, and this causes the rinsing liquor, consistingessentially of pure solvent, to overflow through the slit into thedrying composition. In this way any surface active agent which entersthe rinsing compartment as a result of rinsing of the articles isgradually returned to the drying composition.

A variety of articles were each treated separately as follows. Thearticle was held under a tap until it was thoroughly wet with water. Thewater on the article was usually in the form of droplets and/or a film,and articles of complicated shape contained water in holes and variousundercut portions. The article was immersed in the boiling dryingcomposition for a period of about 30 seconds and was then immersed inthe rinsing compartment containing boiling rinsing liquor again for aperiod of 30 seconds. The drying ability of the composition was testedon a wide variety of articles, particularly on polished metals, lensesand microscope slides. In each case no traces of water were detectableon the treated articles. Moreover, the treated (dried) articles werefree from staining.

During periods when the apparatus was not in use, the composition andthe rinsing liquor were allowed to cool, and 2 percent by weight ofwater, based on the total composition was added to the dryingcomposition which was then stirred until a homogeneous emulsion wasformed. It was found that after drying articles which contained water towhich an electrolyte had been added, a water layer had formed overnighton the surface of the composition. This layer was skimmed off prior tore-use of the composition and it was found that the compositioncontinued to dry articles without causing staining.

EXAMPLE 3 The procedure of Example 2 was repeated except thatperchloroethylene (98 parts) was employed instead of trichloroethylene.

The treated articles (polished metals, lenses and microscope slides)were free from staining and no traces of water could be detected onthem.

The procedure described in Example 2 for eliminating electrolytes fromthe composition was successfully employed in the case of theperchloroethylene composition.

EXAMPLE 4 The cleaning composition described in Example 1 was placed inone compartment of a tank and trichloroethylene (stablized grade) wasplaced in two adjacent compartments of the tank, each colorless. beingprovided with a heater so that the contents could be boiled.

The composition and the pure solvent in the adjacent compartments of thetank were heated to the boil, and glass lenses contaminated with grease,finger marks and general dust were immersed in the boiling compositionfor a period of 60 seconds after which they were withdrawn and immersedin the first tank of boiling solvent to rinse any surface active agentfrom the assemblies. Rinsing was for about 60 seconds, followed by asecond rinse for about 60 seconds in the second tank of boiling solvent.On withdrawal from the second tank the lenses dried rapidly and werefound to be free from contamination.

EXAMPLE 5 The procedure of Example 4 was repeated using instead of thetrichloroethylene composition a composi- The heated articles onwithdrawal from the second tank were dry and completely free fromcontamination.

EXAMPLE 6 This example illustrates the formulation of a waterin-oilemul'sion useful for cleaning a variety of articles. The emulsion wasfound to be stable, even at the boil, and was clear and colorless. Thesolvent was a commercially available stabilized grade oftrichloroethylene.

Parts by Weight 98.2

trichloroethylene calcium tridecyl benzene sulphonate 1.0 water 0.8

EXAMPLES 7-12 These examples illustrate formulations of water-inoilemulsions which are clear and stable and which are useful for cleaning awide variety of articles. The compositions are'stable and colorless,even at the boil. In each example a commercially available (stabilized)Each of these compositions was used successfully to clean a variety ofpolished metals, lenses and microscope slides.

EXAMPLE 13 1.0 parts by weight of ammonium dodecyl benzene sulphonatewas added to 59.5 parts of a commercially available grade oftrichloroethylene containing stabilizers and the mixture was agitated.39.5 parts of distilled water were added and the mixture agitated bymeans of a high speed stirrer for several minutes. The resulting milkyemulsion was then used to clean articles by the following procedure:

The emulsion was placed in a tank and the articles were submerged in theemulsion and agitated for up to 2 minutes. They were then rinsed byagitating in cold trichloroethylene (commercially available gradecontaining stabilizers for about 1 minute, and then further rinsed inboiling trichloroethylene for 1 minute, after which they were withdrawnand dried rapidly. By this procedure a variety of polished metals, glassarticles, and plastic articles were successfully cleaned.

EXAMPLE 14 1.0 part by weight of triethylamine undecyl benzenesulphonate was added to 49.5 parts of a commercially available grade oftrichloroethylene containing stabilizers and the mixture was agitated.49.5 parts of distilled water were added and the mixture was againagitated by means of a high speed stirrer for several minutes. Theresulting milky emulsion was then used to clean articles by thefollowing procedure:

The emulsion was placed in a tank fitted with means for spraying theemulsion on the workpiece at a pressure of about psig. The article wassprayed with the emulsion for up to 2 minutes after which it was rinsedas described in example 13, after which it was withdrawn and driedrapidly- By this procedure a variety of metals, glass and plasticarticles were cleaned.

EXAMPLES 15 and 16 The procedure of example 13 was employed to cleansuccessfully a variety of articles using a composition having theformulation:

*Example 15 -dimethylamine unclecyl benzene sulphonate. Example 16-trimethylamine tridecyl benzene sulphonate.

In these examples, rinsing in both cases was in a commercially availablegrade of 1,1,l-trichloroethane.

EXAMPLE 17 The procedure of example 14 was employed to cleansuccessfully a variety of articles using a composition of theformulation:

Parts by Weight trichloroethylene stabilized 59.5 ammonium dodecylbenzene sulphonate 1.0 distilled water 39.5

What we claim is:

1. A composition for cleaning and drying articles consisting essentiallyof a chlorinated aliphatic hydrocarbon solvent selected from the groupconsisting of trichloroethylene, perchloroethylene, 1,1,1-trichloroethane, beta-trichloroethane, cis and transdichloroethylenesand methylene dichloride, up to 60 percent by weight of water, and from0.1 to 33 percent by weight of an emulsifying agent which is soluble inthe solvent and is selected from the group consisting of calcium,ammonium and primary, secondary and tertiary methylamine and ethylaminesalts of alkyl benzene sulphonic acids wherein the alkyl group containsfrom 1 1 to 13 carbon atoms.

2. A composition as claimed in claim 1 wherein the amount of the salt isat least 1 percent by weight based on the composition.

3. A composition as claimed in claim 1 wherein the solvent istrichloroethylene.

4. A composition as claimed in claim 1 wherein the solvent isperchloroethylene.

5. A composition as claimed in claim 1 wherein the salt of an alkylbenzene sulphonic acid is the calcium salt.

6. A composition as claimed in claim 1 which contains water and whereinthe ratio of the amounts of the salt and water are such that thecomposition is clear and stable.

7. A composition as claimed in claim 1 which contains at least 1 percentby weight of water.

8. A method of cleaning articles which comprises immersing the articlesin a composition as claimed in claim 1, withdrawing the articles andsubsequently rinsing them in a chlorinated aliphatic hydrocarbon solventwhich is the same as that employed in the composition.

9. A method of drying articles which comprises immersing the articles ina composition as claimed in claim 1 which is capable of emulsifyingwater to form a clear water-in-oil emulsion, withdrawing the articlesand subsequently rinsing them in a chlorinated aliphatic hydrocarbonsolvent which is the same as that employed in the composition.

10. A method as claimed in claim 9 wherein the composition initially issubstantially free from water.

1. A composition for cleaning and drying articles consisting essentiallyof a chlorinated aliphatic hydrocarbon solvent selected from the groupconsisting of trichloroethylene, perchloroethylene,1,1,1-trichloroethane, beta-trichloroethane, cis andtrans-dichloroethylenes and methylene dichloride, up to 60 percent byweight of water, and from 0.1 to 33 percent by weight of an emulsifyingagent which is soluble in the solvent and is selected from the groupconsisting of calcium, ammonium and primary, secondary and tertiarymethylamine and ethylamine salts of alkyl benzene sulphonic acidswherein the alkyl group contains from 11 to 13 carbon atoms.
 2. Acomposition as claimed in claim 1 wherein the amount of the salt is atleast 1 percent by weight based on the composition.
 3. A composition asclaimed in claim 1 wherein the solvent is trichloroethylene.
 4. Acomposition as claimed in claim 1 wherein the solvent isperchloroethylene.
 5. A composition as claimed in claim 1 wherein thesalt of an alkyl benzene sulphonic acid is the calcium salt.
 6. Acomposition as claimed in claim 1 which contains water and wherein theratio of the amounts of the salt and water are such that the compositionis clear and stable.
 7. A composition as claimed in claim 1 whichcontains at least 1 percent by weight of water.
 8. A method of cleaningarticles which comprises immersing the articles in a composition asclaimed in claim 1, withdrawing the articles and subsequently rinsingthem in a chlorinated aliphatic hydrocarbon solvent which is the same asthat employed in the composition.
 9. A method of drying articles whichcomprises immersing the articles in a composition as claimed in claim 1which is capable of emulsifying water to form a clear water-in-oilemulsion, withdrawing the articles and subsequently rinsing them in achlorinated aliphatic hydrocarbon solvent which is the same as thatemployed in the composition.